1. Field of the Invention
The present invention relates to a wavelength selectable laser oscillator in wavelength tunable laser, and more particularly to a wavelength selectable laser oscillator in wavelength tunable laser by which highly repeated oscillation of laser beam in a laser resonator can be realized.
2. Description of the Related Art
As a wavelength tunable laser which directs to realization of pulsed oscillation in a laser resonator for laser beam, for example, a flash-lamp-excitation Q-switch YAG laser excited titanium-sapphire (Ti:Al.sub.2 O.sub.3) laser has heretofore been known.
In a flash-lamp-excitation Q-switch YAG laser excited titanium-sapphire laser, the pulse repetition rate is determined by the rate of lighting the flash-lamp, since the YAG laser is operated by a Q-switch-pulsed mode based on flash-lampexcitation.
In these circumstances, since the rate of lighting a flash-lamp is usually around 1 Hz to 50 Hz, there is a limit for increasing the pulse repetition rate of the laser that was excited by the aforesaid flash-lamp excitation laser. Accordingly, there is a need for a wavelength tunable laser by which much higher rates of pulse repetition can be achieved for laser beam.
Furthermore, the aforesaid flash-lamp excitation Q-switch YAG laser excited titanium-sapphire laser requires high excitation input (in general, around 20 mJ/pulse is required as the excitation energy), and the wavelength tuning speed thereof is low, so that it involves a problem of having poor flexibility in case of practicing the laser.